1. Field of the Disclosure
The present disclosure relates to a power amplification module.
2. Description of the Related Art
A power amplification module is used in a mobile communication device such as a cellular phone in order to amplify the power of a signal to be transmitted to a base station. In recent years, modulation schemes such as high-speed uplink packet access (HSUPA), long term evolution (LTE) and LTE-Advanced, which are high-speed data communication standards, have been adopted in cellular phones. In these communication standards, it is important that shifting and distortion of phase and amplitude be made small in order to improve the communication speed. In other words, high linearity is demanded for a power amplification module. In addition, in these communication standards, the range over which the amplitude of a signal changes (the dynamic range) is often widened in order to improve the communication speed. A high power supply voltage is necessary in order to achieve high linearity in the case of a large dynamic range and the power consumption of the power amplification module tends to be high.
On the other hand, it is demanded that power consumption be reduced in cellular phones in order to lengthen the amount of time for which telephone calls and communications can be performed. In Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-513943 for example, a power amplification module is disclosed in which an envelope tracking (ET) scheme is adopted that improves power efficiency by controlling the power supply voltage in accordance with the amplitude level of an input-modulated signal. In addition, a power amplification module is also known in which an average power tracking (APT) scheme is adopted that controls the power supply voltage in accordance with the average output power.
In such power amplification modules that employ the envelope tracking scheme or the average power tracking scheme, a DC-DC converter is used in order to change the power supply voltage. Consequently, the reception band noise characteristics of the power amplification module may be degraded due to noise output from the power supply circuit at the time of the envelope tracking operation or the average power tracking operation.